On the Chile side, PUQ (Punta Arenas) is the main airport. LAN is the country's main airline, and you qualify for the South America airpass if you fly in on LAN or another One World carrier. Otherwise, airfare can be quite high. Or, it may not add much to your ticket if it is all part of the same ticket. LAN has nonstop service JFK/SCL certain days of the week, so it makes it an easy trip. You might also consider the Lakes region as part of your trip (fly to PMC - Puerto Montt).

Note that if you are flying on national flights within Argentina, you will arrive @ EZE (from the US or other points in South America) and then have to take a bus to AEP, the domestic city airport, which requires several hours' connection time.

I have never been to the south of Argentina, so I can't help you out there. Whatever you decide, I'm sure you will have a great trip.

http://www.lan.com/promociones/data/...nas-en-us.html

These fares are really good. SCL/PUQ alone can be several hundred $.